ATEX and Spark-Resistant Axial Fans: Zones, Categories and AMCA 99

Fans that handle or operate near flammable gas, vapour, or combustible dust must be selected with the hazard in mind, and two different systems are often confused for one. ATEX classifies equipment for use in explosive atmospheres by group, category, and zone. AMCA 99 describes three levels of spark-resistant construction. They are not interchangeable, and neither replaces a proper assessment of the hazard. This guide sets out what each means and what to specify.

NextAir Systems does not currently manufacture ATEX-certified or AMCA 99 spark-resistant fans. We include this guide because specifying these fans correctly protects your plant, and because it shows where a standard fan is and is not acceptable.

Start With the Hazard, Not the Fan

The hazardous area is classified by the plant owner or operator, normally through a hazardous-area study, and that zoning is the end user’s responsibility, not the fan supplier’s. Zones describe how often an explosive atmosphere is present.

Gas	Dust	Definition (typical)
Zone 0	Zone 20	Hazard present in normal operation or for long periods, typically over 1,000 hours a year
Zone 1	Zone 21	Hazard likely in normal operation, typically 10 to 1,000 hours a year
Zone 2	Zone 22	Hazard not likely in normal operation and, if it occurs, present only briefly, typically under 10 hours a year

The atmosphere can be inside the fan, meaning the gas being conveyed, outside it, or both. The fan may need to be suitable for the zone inside and the zone outside, and these can be different.

ATEX Groups and Categories

ATEX equipment is split into two groups. Group I is equipment for underground mining and its surface installations exposed to firedamp or combustible coal dust. Group II is equipment for other places where explosive atmospheres may form.

Within Group II, categories 1, 2, and 3 give decreasing levels of protection. Category 1 suits zones 0 and 20, category 2 suits zones 1 and 21, and category 3 suits zones 2 and 22. The letter G denotes gas and D denotes dust. Group I mining equipment uses categories M1 and M2 instead.

Zone (gas / dust)	Category	Equipment protection level	Ignition sources considered
0 / 20	1	Ga / Da	Normal operation, expected malfunction, and rare malfunction
1 / 21	2	Gb / Db	Normal operation and expected malfunction
2 / 22	3	Gc / Dc	Normal operation

Reading an ATEX Marking

A typical marking reads something like: II 2G Ex h IIB T4 Gb. The elements mean:

• II: equipment group, here surface industry.
• 2G: category 2 for gas, suitable for zone 1.
• Ex h: the protection concept for non-electrical equipment.
• IIB: gas group, where IIA is typified by propane, IIB by ethylene, and IIC by hydrogen.
• T4: temperature class, the maximum surface temperature. T1 corresponds to 450 °C, T2 300 °C, T3 200 °C, T4 135 °C, T5 100 °C, and T6 85 °C.
• Gb: the equipment protection level.

A fan for a hazardous area must be marked for the gas group and temperature class of the gas it handles. A fan suitable for IIB gas is not necessarily suitable for hydrogen.

EN 14986: The Design Standard for Fans

EN 14986 specifies constructional requirements for fans in Group II, gas categories 1, 2, and 3, and dust categories 2 and 3, intended for explosive atmospheres. It covers design, construction, testing, and marking. Important limits on its scope:

• It does not apply to Group I fans, meaning fans for mining. Those fall under other standards, including EN ISO 80079-38 and EN 1127-2.
• It does not cover explosion group IIC other than hydrogen, or category 1D fans.
• It does not apply to cooling fans or impellers on rotating electrical machines or engines.

The standard also defines standard operating conditions, commonly summarised as ambient pressure of about 0.8 to 1.1 bar, intake temperature between −20 and +60 °C, oxygen content up to 21%, and a limit on the energy delivered to the air, equivalent to a pressure rise on the order of 30,000 Pa. Our axial fans reach 2,400 Pa, well below that. Operating outside the defined conditions needs a separate assessment.

Many fans can be conformity-assessed by the manufacturer without mandatory third-party certification, depending on category. That does not remove the buyer’s responsibility to check that the fan and documentation suit the zone.

AMCA 99: Spark-Resistant Construction

AMCA 99 gives a classification for spark-resistant construction, in three levels.

Type	Requirement in summary
A	Non-ferrous material for the whole airstream, with extra locking to stop the impeller and shaft shifting
B	Non-ferrous impeller and a non-ferrous rub ring around the shaft opening, with the same extra locking
C	Constructed so that a shift of the impeller or shaft cannot bring two ferrous parts into contact

For all types, bearings and electrical devices must be kept out of the airstream, and the fan must be earthed to prevent static build-up. Aluminium is a common material, but the standard warns that aluminium rubbing on rusty steel can itself produce sparks, so steel surfaces must be kept clean.

What AMCA 99 Does Not Do

AMCA 99 is general in nature, does not require qualification testing, and is written for applications where the explosive material is inside a sealed, ducted airstream and not present outside the casing. Manufacturers’ notes on the standard state that spark-resistant construction does not guarantee safety, and does not protect against ignition caused by catastrophic failure or by anything in the airstream. It is a construction classification, not an ATEX certification, and using it does not make a fan ATEX-rated.

Motors and Other Parts

The fan is only one component. An electric motor in a hazardous area needs its own suitable protection. Sensors, drives, and cables must also be suitable, and belts should be anti-static where used. A motor cooled by the airstream is inside the atmosphere the fan handles, so it must suit that zone.

What to Provide When You Specify

1. Zone, inside and outside the fan, for gas and for dust.
2. Gas or dust group, and the ignition temperature or temperature class required.
3. Intake temperature, pressure, and oxygen content.
4. Whether the requirement is ATEX equipment or AMCA 99 spark-resistant construction, or both.
5. Whether it is a mining application, which is Group I.
6. Documentation required, such as declaration of conformity and marking.

Where NextAir Systems Fits

NextAir Systems does not currently manufacture ATEX-certified or AMCA 99 spark-resistant fans. For any fan that sits inside a classified zone, or that handles a flammable gas, vapour, or dust, buy an ATEX-marked fan from a specialist supplier and use the checklist above to specify it.

A standard fan is only appropriate where the fan and its motor sit outside any classified zone and the air being handled is not explosive. Whether a fan position is classified is decided by the plant’s hazardous-area study, not by the fan supplier, so confirm it there first.

Where those conditions are met, we can help with the rest of the job: sizing the airflow, checking the operating point, and supplying axial fans up to 1,600 mm impeller diameter, 2,400 Pa static pressure, and 185,000 m³/h. If a duty falls outside what we can supply, we will say so plainly instead of forcing a selection.

Check Whether a Standard Fan Is Acceptable

Send your layout and zone classification, and we’ll tell you plainly whether a standard fan can serve a non-classified position or whether you need a specialist supplier. Contact us for a free quote.

Frequently Asked Questions